1. Field of the Invention
The present invention relates to an open cable set-top box of which a point of deployment (POD) is separated from a main circuit unit, and more particularly to an open cable set-top box diagnosing system in which the POD, separated from a main circuit unit, has a newly defined interface that is used to check an operation state of an open cable set-top box, transmits the checked state to a predetermined server, according to which the operation state of the open cable set-top box is diagnosed, and a method thereof.
2. Description of the Background Art
Recently, a digital cable set-top box became popular. The set-top box is connected to a cable head end through a cable and produces a program for a digital cable. The digital cable set-top box makes a bidirectional communication with the cable head end in a manner that it receives an A/V broadcast program from the cable head end through an inband (IB), and transmits a user's request to the cable head end through an out of band (OOB) and receives a corresponding service to be displayed.
FIG. 1 is a schematic block diagram showing a construction of a conventional digital cable set-top box. As shown in the drawing, a digital cable set-top box 100 includes a tuner 11 for tuning a receive frequency to be able to receive an A/V broadcast program corresponding to a frequency of a channel desired by a user from a cable head end (not shown); a QAM (Quadrature Amplitude Modulation) demodulator 12 for receiving and demodulating an A/V broadcast program tuned by the tuner 11; a conditional access unit (CAU) 14 for receiving the demodulated signal from the QAM demodulator 12 according to a pre-set condition; a TP (transport) demultiplexer 16 for processing the signal outputted from the CAU 14 and outputting a data stream; an MPEG decoder 18-1 and an AC-3 decoder 18-2 for decoding the data stream outputted from the TP demultiplexer 16 and outputting video signals and audio signals; an OOB processing unit 13 for receiving the broadcast program information, such as a channel tuning or a program guidance from the tuner 11 through the OOB and processing it; and a CPU 17 for receiving the signal processed by the OOB processing unit 13 and controlling the CAU 14 and the TP demultiplexer 16.
The OOB processing unit 13 includes an OOB receiver 13-1 for receiving the signal outputted from the tuner 11; an OOB protocol processor 13-3 for processing a protocol of the signal processed by the OOB receiver 13-1 and outputting it to the CPU 17; and an OOB transmitter 13-2 for processing the signal outputted from the OOB protocol processor 13-3 and outputting it to the tuner 11.
The operation of the digital cable set-top box of the conventional art constructed as described above will now be explained.
When power is supplied to the digital cable set-top box, the tuner 11 receives an A/V broadcast program signal from the cable head end, tunes its frequency so as for a user to receive the A/V broadcast program, and outputs the tuned A/V broadcast program signal to the QAM demodulator 12. Then, the QAM demodulator 12 QAM-demodulates the A/V broadcast program signal and the QAM-demodulated signal to the CAU 14.
After the CAU 14 receives the QAM-demodulated signal, in case that the QAM-demodulated signal is in a scrambled state, the CAU 14 descrambles the QAM-demodulated signal according to a conditional access key (CAK) outputted from the CPU 17 and outputs it to the TP demultiplexer 16.
Then, the TP demultiplexer 16 separates a video packet and an audio packet of the descrambled signal and outputs them to the video decoder 18-1 and the audio decoder 18-2.
The video decoder 18-1 clears an overhead (i.e., various header information or starting code, etc.) from the video packet and performs variable-length decoding (VLD) for the pure data information. Then, the decoded information undergoes inverse-quantizing, inverse-discrete cosine transforming and motion compensating using a motion vector. The video-signal is restored as a pixel value of the original screen and outputted to the monitor.
The audio decoder 18-2 decodes the audio packet and outputs it to a speaker, by using an AC-3 algorithm.
Subscriber managing server systems connected with the cable head end manages subscribers connected with the cable head end, receives subscriptions from subscribers who desire to receive a paid program provided for a paid TV or a pay-per-view and transmits information corresponding to the paid program to the subscribers, and manages and operates the network on the whole.
When the subscriber registers at the subscriber managing server system, he or she is given a password from the subscriber managing server system. The paid program is provided from the head end to the set-top box as the subscriber inputs the password to the set-top box.
The subscriber managing server system renders the head end to transmit a diagnosis command signal to the set-top box 100, thereby diagnosing the operation state of the subscriber's set-top box. That is, when the OOB receiver of the set-top box receives the diagnosis command signal from the head end, the set-top box performs its own self-diagnosis program to diagnose whether there is an error in each circuit unit of the set-top box and transmits the diagnosis result to the head end through the OOB transmitter.
Upon receipt of the diagnosis result of the set-top box, the head end transmits the diagnosis result to the subscriber managing server system and receives an instruction from the subscriber managing server system as necessary.
Since the communication standard is already set, the set-top box is manufactured by a set-top box manufacturers in cooperation with a cable system operator (SO). Accordingly, the cable SOs install the set-top box only for the subscribers who order it. Thus, problems arise that it is difficult to control production of the set-top box, there is a problem of an inventory burden, and the set-top box is to be replaced whenever the function of the set-top box is upgraded.
In order to solve the problems, the cable SOs set a standard, such as an ‘open cable’, for separating the CAU from the main circuit unit and manufactures a set-top box without the CAU.
In detail, the open cable set-top box of the above description is manufactured in a manner that the point of deployment (POD) including the CAU that has been installed in the cable set-top box is separated from the main circuit unit of the set-top box. A standard interface protocol between the main circuit unit of the set-top box and the POD is defined, and an interface is included between the main circuit unit and the POD.
Accordingly, the set-top box manufacturer can manufacture the open cable set-top box without a restriction, and users also can purchase the open cable set-top box without a restriction.
Accordingly, the users may purchase the open cable set-top box and the POD provided by the cable SOs and connect them, thereby viewing cable broadcasting.
FIG. 2 is a schematic block diagram showing a construction of an open cable set-top box in accordance with the conventional art, which includes a main circuit unit 200, a point of deployment (POD) module 300 and an interface 201 for connecting the main circuit unit 200 and the POD module 300.
The main circuit unit 200 includes a tuner 21 for tuning a receive frequency to be able to receive an A/V broadcast program corresponding to a frequency of a channel desired by a user from a cable head end (not shown); a QAM (Quadrature Amplitude Modulation) demodulator 22 for receiving an A/V broadcast program tuned by the tuner 11, demodulating it and outputting the demodulated QAM signal through the interface 201 to the POD module 300; a TP (transport) demultiplexer 24 for processing the signal received through the interface 201 from the POD module 300 and outputting a data stream; an MPEG decoder 26-1 and an AC-3 decoder 26-2 for decoding the data stream outputted from the TP demultiplexer 24 and outputting video signals and audio signals; an OOB receiver 23-1 for receiving the broadcast program information such as a channel tuning or a program guidance from the tuner 21 through the OOB, processing and outputting it through the interface 201 to the POD module 300; an OOB transmitter 23-2 for receiving the signal through the interface 201 from the POD module 300 and outputting it through the OOB to the tuner 21; and a CPU 25 for controlling each circuit unit of the main circuit unit 200 and communicating with the POD module 300 through the interface 201.
The POD 300 includes a local CPU 34 for communicating with the CPU 25 of the main circuit unit 200 and controlling the whole POD; a CAU 33 for receiving the demodulated QAM from the QAM demodulator 22 of the main circuit unit 200, and descrambling the QAM-demodulated signal according to a conditional access key (CAK) outputted from the CPU 34 and outputting it to the TP demultiplexer 24 in case that the QAM-demodulated signal is in a scrambled state; an OOB protocol processor 31 for communicating with the OOB receiver 23-1 and the OOB transmitter 23-2 under the control of the CPU 34; and a TP demultiplexer 32 for receiving the demodulated QAM and the signal from the OOB protocol processor 31 and demultiplexing them.
The POD module 300 shown in FIG. 2 is in the form of a PCMCIA card.
The operation of the conventional open cable set-top box constructed as described above will now be explained.
When power is supplied to the open cable set-top box, an A/V broadcast program is inputted to the POD module 300 through the tuner 21 and the QAM demodulator 22, and the CAU 33 of the POD module 300 descrambles and outputs the A/V program to the TP demultiplexer 24 of the main circuit unit 200. In other words, the CPU 34 of the POD module 300 interprets the command received from the head end through the OOB transmitter 23-2 and OOB receiver 23-1 of the main circuit unit 200 and the OOB protocol processor 31 and the TP demultiplexer 32 of the POD module 300 and outputs the interpreted command through a data channel and an extended channel of the interface 201 to the CPU 25 of the main circuit unit 200, so that the CPU 25 performs the command instructed by the head end.
Alternatively, the CPU 34 of the POD module 300 transmits a request of a user through the OOB transmitter 23-2 and the OOB receiver 23-1 of the main circuit unit 200 and the OOB protocol processor 31 and the TP demultiplexer 32 of the POD module 300 to the head end, so that the user may receive his or her desired program.
FIG. 3 shows a communication protocol between the CPU of the POD and the CPU of the main circuit unit transmitted via the data channel. As shown in the drawing, the communication protocol includes, from the bottom, a PC card physical layer, a PC card link layer, a PC card transport sublayer, a generic transport sublayer and a session layer, which are common with other communication protocol, and a resource layer which has different contents. The resource layer gives and takes a software module such as an object to and from other layers to support execution of applications arranged at the upper portion of the resource layer.
The application performs the communication between the POD module 300 and the main circuit unit, 200 using resources included in the resource layer. Thus, whether the function of the POD interface can be extended is determined depending on how the resources are defined.
For example, the below Table 1 shows kinds of resources defined in the current U.S. open cable standard.
TABLE 1ResourceDVS064 Part BOpen CableResource ManagerYesYesMMIYesYesApplication informationYesUpdatedLow Speed CommunicationYesUpdatedConditional Access SupportYesYesSmart Cart ReaderOptionalOptionalCopy ProtectionNoYesHost Control-info. ResourceYesUpdatedExtended Channel SupportNoYesGeneric IPPV SupportNoYesSpecific Application SupportNoYes
As shown in Table 1, the resources are defined only to support applications used by users without including any resources to diagnose a defective state or a defective condition of the set-top box.
Thus, because the open cable set-top box being on the market does not include such a resource having a diagnostic function in the POD interface, it is not possible for the POD module 300 to diagnose itself or the main circuit unit 200 to determine whether or not the set-top box is out of order.
In addition, in case that the open cable set-top box is out of order and thus the user is not able to view a desired broadcast program, since the user has no idea of which one of the POD module and the main circuit unit of the set-top box has been rendered inoperable the user cannot determine whether to report he problem to one of the cable SO or the set-top box manufacturer.
Therefore, since the head end, which provides the service to the open cable set-top box, is unable to recognize the disorder of the subscriber set-top box in advance, its competitive edge is degraded with respect to the satellite broadcast producers and ground wave broadcast producers.